Sewing machine having thread severing device

ABSTRACT

A sewing machine comprises a machine frame having a workpiece support and a bracket which is pivotally mounted on the frame for pivotal upward movement to a rest position and downward movement to an operative position. The machine includes a rotatable shuttle mounted on the bracket in a position overlying a needle which is mounted for reciprocation upwardly and downwardly in the frame below the shuttle. A clamping arm is pivoted on the frame below the bracket and includes a portion which is engageable with a cutting mechanism carried on a pressure plate which is supported on the bracket. Movement of the bracket causes movement of the clamping arm to actuate the cutting mechanism to sever the thread. The cutting mechanism is carried on a pressure plate which is suspended on a rod having a pin portion which is confined for movement in a vertical slot carried on a holder mounted on the bracket. The upward movement of the bracket initially causes a displacement of the shuttle away from the workpiece so that the thread is drawn upwardly and a further movement causes movement of the clamping arm to actuate the cutting mechanism to sever the thread after the pressure plate lifts off the workpiece which is supported on the frame.

[ Nov. 12, 1974 United States Patent [1 1 Tolle SEWING MACHINE HAVINGTHREAD a workpiece support and a bracket which is pivotally SEVERINGDEVICE mounted on the frame for pivotal upward movement to a restposition and downward movement to an op- [76] Inventor: Gunter Tolle,Wendelinusstrasse I5,

752 Bruchsal 4, Germany Dec. 20, 1973 erative position. The machineincludes a rotatable shuttle mounted on the bracket in a positionoverlying [22] Filed:

a needle which is mounted for reciprocation upwardly and downwardly inthe frame below the shuttle. A [211 App]' NO"426605 clamping arm ispivoted on the frame below the v bracket and includes a portion which isengageable Foreign Application Priority Data with a cutting mechanismcarried on a pressure plate which is supported on the bracket. Movementof the Jan. 1973 Germany............................ 2300042 bracketcauses movement of the clamping arm to ac tuate the cutting mechanism tosever the thread. The

cutting mechanism is carried on a pressure plate which is suspended on arod having a pin portion which is confined for movement in a verticalslot car- 02 0 60 6 2 2 N60 9 Hb om OM6 7 U I l u mfi 2 5 2 a m 19 2m Q1 u H/ l n "2 .n "HU mmh Hr H .1 f C d SLd n. UIF Ill. 2 00 .355. Ill

ried on a holder mounted on the bracket. The upward movement of thebracket initially causes a displace- [56] References Cited UNITED STATESPATENTS ment of the shuttle away from the workpiece so that the threadis drawn upwardly and a further movement 2.499.335 2/1950 Spaine112/252causes movement of the clamping arm to actuate the cutting mechanism tosever the thread after the pres- 2,509,619 Vollman 3,512,491 3.749041Heimann et a1. Bowint.n...........

sure plate lifts off the workpiece which is supported on the frame.

Primary E.raminerWerner H. Schroeder Attorney, Agent, or FirmMcGlew andTuttle [57] ABSTRACT v A sewing machine comprises a machine frame having6 Claims, 6 Drawing Figures mrllllL SHEET 1 BF 2 PATENTEDHUV 12 19MFig.7

SEWING MACHINE HAVING THREAD SEVERIN DEVICE BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates in general tothe construction of sewing machines and, in particular, to a new anduseful sewing machine which includes a rotatable shuttle mounted on abracket which is pivotally mounted on a frame carrying the needle whichreciprocates upwardly and downwardly in the frame from below theworkpiece support in cooperation with the shuttle and which includesmeans for severing the thread when the sewing machine is stopped and thearm is moved to a nonoperative or rest position.

2. Description of the Prior Art The present invention relates to sewingmachines of a type having a rotating shuttle provided above the tablefor the sewn material and received in a bracket which is movable from aworking position into a rest position; a needle cooperating with theshuttle, and adapted to pass through the sewn material from beneathupwardly, and a material clamping arm movable from a clamping positioninto a rest position.

To sew so-called purl stitched buttonholes, it is known to use sewingmachines in which the shuttle is located above the table receiving thesewn material and the needle penetrates the material from beneathupwards. Since in machines of this type, the bracket receiving theshuttle requires much more space than a usual bracket receiving theneedle and must be positioned during the stitching very close above thematerial to ensure a faultless stitch, it is a common practice thatafter the stitching cycle, the bracket is brought back from its workingposition into a rest position which is distant from the stitching area.Before removing the bracket, however, it is necessary to draw off andcut the thread extending between the upper surface of the sewn materialand the thread bobbin of the shuttle.

SUMMARY OF THE INVENTION The invention provides a thread cuttingmechanism for sewing machines of the mentioned type, which comesautomaticallyinto effect at the end of the sewing operation while thebracket is moving from its working into its rest position, assuring avery short end portion of the thread remaining with the sewn materialand avoiding the necessity of using both a special thread puller and aparticular drive and control means for the cutting tool.

In accordance with the invention, the sewing machine includes a driveconnection operating with an idle stroke and interconnecting the bracketreceiving the shuttle with the clamping arm for the sewn material and adrive mechanism for a cutting tool which, in a well-known manner, iscarried on the clamping arm and actuated by the motion of the bracket.The idle stroke of the drive connection between the bracket and theclamping arm has the effect that at the end of the sewing operation, thebracket is first lifted from the material and the clamping arm up to acertain distance, while the clamping arm remains applied against thematerial, whereby the thread is pulled off the shuttle in a lengthcorresponding to the length of the idle stroke. At the end of the idlestroke, while the bracket continues to move towards its rest position,the bracket motion is transmitted to the cutting tool which is mountedon the clamping arm. Thus, both the beginning and the execution of thecutting operation proper is automatically derived from the necessarymovement of the bracket and the thread is cut off close to the surfaceof the material. Still another advantage results therefrom, namely, thatboth the pulling off and the cutting of the thread is effected duringthe motion of the bracket from its working into its rest position sothat the operational cycle of the sewing machine can be considerablyreduced.

Advantageously, to obtain an idle stroke between the bracket and theclamping arm and coordinate the cutting operation with the bracketmotion, there is provided a claw engaging the clamping arm from beneathand movable relative thereto within limitsand against the action of aspring and, as the drive means for the cutting tool, a ratchet levermounted on the bracket for cooperation with a crank having the shape ofa pawl and forming part of a'four-bar linkage hinged on the clamping armand including a swinging member carrying the cutting blades is provided.

To be able to adjust the time of the thread cutting and thereby thethread length to be pulled off within certain limits in respect to themotion of the bracket, there is provided in accordance with adevelopment of the invention, the mounting of a ratchet lever on abridge, which is supported on the bracket and whose relative positionthereto is adjustable.

Accordingly, it is an object of the invention to provide an improvedsewing machine of a type which includes a bracket or arm which ismounted on a machine frame for pivotal movement upwardly to a restposition and downwardly into pressing engagement with the material on asupport of the frame and which includes a rotatable shuttle mounted overa reciprocating needle which is carried in theframe below the workpiecesupport and which includes a clamping arm which engages the workpieceand which is moved by movement of the bracket to actuate a cuttingmechanism to cut away the thread when the bracket is moved to a restposition.

A further object of the invention is to provide a sew ing machine whichincludes a rotatable bobbin mounted above the reciprocating needle of asewing machine frame and which includes a clamping arm arranged belowamovable bracket carrying the bobbin which holds the workpiece as thethread is drawn upwardly therethrough during the time in which thebracket is moved to a rest position and thereafter actuates a cuttingmechanism to cut the thread close to the material and to leave a lengthof thread remaining in the bobbin for the formation of a new loop whenthe machine is again operated.

A further object of the invention is to provide a sewing machineconstruction which is simple in design, rugged in construction, andeconomical to manufacture.

For an understanding of the principles of the invention, reference ismade to the following description of a typical embodiment thereof asillustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevational view of a stitch-group sewing machineconstructed in accordance with the invention;

FIG. 2 is a partial elevational view of the mechanism shown in FIG. 1with the bracket in a lifted position;

FIG. 3 is a view similar to FIG. 2 with the bracket in a complete restposition;

FIG. 4 is a section taken along the line IVIV of 5 GENERAL DESCRIPTIONOF THE PREFERRED EMBODIMENT Referring to the drawings in particular, theinvention as embodied therein, comprises a sewing machine, which forexample, may be a stitch-group buttonhole sewing machine, comprising astationary substructure or frame 1, with a bracket or arm 2 pivotallymounted thereon at the location of a pivot pin 3. To move the bracketfrom a working position into a rest position, a double-actionelectromagnet 4 is provided in the substructure 1, whose armature isconnected to a portion of the bracket 2 lateral to the pivot 3. Both theworking and the rest position is fixed by corresponding nonrepresentedstops.

A main shaft 5 is mounted in the substructure l of the sewing machine,and carries a pulley 6, driven by a stop motor (not shown). A crank 7,mounted on the free end of shaft 5, drives a needle bar 11, carrying athread guiding needle 10, through a link 8 and an intermediate member 9.Needle 10 pierces the sewn material from beneath upwards and cooperateswith a rotating shuttle 12 which is mounted on the end surface ofbracket 2.

A pulley 13 on the main shaft 5 transmitting motion through a toothedbelt 14 and another pulley 115 drives a shaft 16 mounted in the bracket2 and, therefrom, through a pair of bevel gears 17, a vertical shaft 18,and

7 another pair of bevel gears 19 to the shaft 20 of the shuttle 12. Bymeans of this drive train, shuttle 12 is driven at a double speed withrespect to the reciprocating motion of the needle.

In the present example, the sewing machine is provided with a support 21for the material to be sewn.

The support 21 is pivotally mounted at 22 and backed up, in thestitching area, by a slidable rest 23, both the pivot 22 and the rest 23being supported by the substructure 1. The rest 23 comprises a bolt 24which is biased by an adjustable spring 25 and movable within a distancepredetermined by astop 26. On the support 21 is a plate 28 provided,which is shiftable in the direction of the longitudinal axis of themachine by means of a worm gear 29 and in a manner not specificallyshown. The material to be sewn is placed on surface 27 of plate 28. Theworm gear 29 is driven by a toothed belt 32 carries a rail 42, asparticularly seen in FIG. 4, which extends in the advance direction ofthe clamping arm. A pressure roller 43 mounted for free rotation in a acarrier 44 is adapted to ride on rail 42. Carrier 44 is rigidlyconnected to rod 45 which is slidably received in guide hole 47 of lug46 provided on bracket 2. Spring 48 is mounted between the lug 46 andcarrier 44 urging thepressure roller 43'per'manently downwards, thetraveling distance of the carrier 44 being limited by a pin 50projecting from sliding rod 45 and guided in an oblong slot 49 of lug46. Carrier 44 is further provided with a claw 51 engaging the pressurepiece or the rail from beneath and with an angle stop for engagingbracket 2.

The cutting mechanism or the thread comprises a swinging member 54 (seeFIGS. 4, 5 and 6), pivoted on a pin 53 which is provided on the tenter40. The free end of the swing member 54 is formed with a cutting blade55. Counterblade 56 cooperating therewith is a piece which is pivotallymounted on a pin 57 provided on swinging member 54 and which is formedwith two toes 58, 59 cooperating with a stop piece 60 secured to tenter40, in a manner described hereinafter. To improve the cuttingreliability, a flat spring 62 applying against the Counterblade 56 issecured to a pin 61 provided on the swinging member 54.

The cutting tool comprising the 'bladesSS, 56 .is actuated by means of aconnection lever 63 whose other end is hinged to crank 64 (FIGS. 1 to 3)which is pivotally mounted on pin 65 provided on the clamping arm 38 andretained in its initial position by worm spring 66. Crank 64, connectionlever 63, swinging member 54 and the two pins 53 and 65 form a four-barlinkage. As

passed around two pulleys 30, 31 and receives its moterial to be sewnagainst surface 27. The tenter 40 is provided with a slot 41 to permitthe passage of the needle 10 and of a buttonhole gauge. Pressure piece39 may be seen in FIGS. 1 to 3, crank 64 is'formed with a nose 67, andserves simultaneously as a pawl for ratchet lever 68 which is pivotallymounted on pin 69 provided on bridge 70. Ratchet lever 68 is held in theposition shown in FIG. 1 by means of a worm spring 71 and is formed withan arm 72 adapted to apply against stop pin 73 which is provided onbridge for limiting the pivotal motion of ratchet lever 68. Bridge-70,which has an angular cross-section, is mounted tiltable about pin 74provided on bracket 2, and can be adjusted in a desired position bymeans of two set screws 75, 75 which are received in support 76 securedto bracket 2 and apply against the upper surface of bridge 70, theposition of the latter being given by the length of engagement of thescrews.

The sewing machine operates as follows:

During the sewing operation, the bracket 2 is fixed in its workingposition (FIG. 1); the sewn material is placed between the surface 27and the tenter 40 of clamping arm 38. By the action of spring 25provided in substructure 1, support 21, and thereby surface plate 27 ofplate 28, is pressed against tenter 40. Angle stop 52, provided oncarrier 44, applies against the bottom surface of bracket 2; and spring48, having a flatter characteristic than spring 25, is compressed. Atthe end of the sewing operation, the machine is stopped in the lowermostposition of needle l0'and the electromagnet 4 is energized.

The needle thread extends between the bottom side of the sewn materialand the needle and the shuttle thread extends between the upper side ofthe sewn material and the shuttle or the shuttle bobbin.

As soon as bracket 2 begins to execute its motion about pivot 3, fromthe working into the rest position,

spring expands first. Therefore, the angle stop 52 remains appliedagainst the bottom side of bracket 2 and support 21 along with thesurface 27 as well as the clamping arm 38 mounted thereon execute apivotal movement about the pivot 22. During this motion, the relativeposition of the sewn material and the shuttle l2 and of the clamping arm38 and shuttle 12 is not changed. Once the support 21 has reached itsend position, as determined by stop 26, bracket 2 begins to move awayfrom the surface 27 while continuing its pivotal movement about pivot 3.At this moment,

spring 48 begins to expand and the sliding rod 45 is shifted in lug 46of bracket 2 relative to the latter. Since the pressure roller 43applies against rail 42, the sewn material is still clamped during thisrelative motion and, because shuttle 12 is moved away from the material,a length of thread corresponding to the increased distance is drawn offthe shuttle bobbin (FIG. 2), Meanwhile, the ratchet lever 68 engagesfrom beneath the nose 67 of crank 64 and imparts to the latter a pivotalmotion about pin 65 and against the action of worm spring 66. Thispivotal motion is transmitted by connection lever 63 to swinging member54 which, consequently, swivels about pin 53 (FIGS. 5 and 6) and bringscutting blade 55, formed at its extremity, into the cutting position.During the further relative motion between bracket 2 and clamping arm38, swinging member 54 continues to turn about pin 53. Toe 58 ofcounterblade 56 comes then to apply against the stop piece 60 andexecutes a pivotal movement relative to swinging member 54, about thepin 57 fixed to the latter. Thereby, cutting blade 55 and counterblade56 move against each other and cut the thread extending between the sewnmaterial and the shuttle bobbin close above the upper surface of thematerial (FIG. 6). This cutting operation takes place at the end of the,relative movement of bracket 2 and clamping arm 38 so thatthe threadportion remaining, attached to the shuttle after the cutting, issufficiently long to permit the formation of the initial stitches in thenext sewing cycle. Also, because clamping arm 38 is still resting uponthe sewn material, favorable conditions for the cutting operation areensured.

During the following continuing pivotal movement of bracket 2, theclamping arm 38 is taken along upwards by claw 51 engaging from beneathrail 42; thus, the arm 38 turns about pivot 37. Thereby, ratchet lever68 and pawl 67 are disengaged, and arm 72 of lever 68 abuts against pin73 (FIG. 3). As soon as crank 64 and lever 68 are disengaged, the wormspring 66 is released and returns the four-bar linkage formed by crank64, the connection lever 63 and swinging member 54 into the initialposition. Toe 59 of counterblade 56 applies against stop piece 60 fixedto tenter so that counterblade 56 is pivoted about pin 57 in thecounterclockwise direction and swing member 54, under the action of wormspring 66, is pivoted about pin 53 and returns into its initialposition.

To bring the bracket 2 from its rest position back into its workingposition, the electromagnet is energized again. Bracket 2 takes clampingarm 38 along in the downward direction until tenter 40 comes to restupon the sewn material. Since the characteristic of spring 48 is flatterthan that of spring 25, during the continuing downward movement ofbracket 2, spring 48 is compressed first and angle stop 52 appliesagainst the bottom surface of bracket 2. Pressure roller 43, restingupon rail 42, presses tenter 40 against, surface 27 of plate 28, andsupport 21 is thereby urged to pivot about 22 and overcome the force ofspring 25. The downward movement of bracket 2 continues until it reachesand is fixed in its working position predetermined by a stop.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A sewing machine comprising a machine frame having a workpiecesupport, a bracket mounted on said frame for pivotal movement upwardlyto a rest position and downwardly to an operative position, a needlemounted on said frame for upward and downward reciprocation below saidsupport, a rotatable shuttle mounted on said bracket overlying saidneedle for cooperative engagement therewith, a clamping arm connected tosaid bracket for movement therewith and pivoted on said frame over saidsupport and having an end adapted to clamp the workpiece on the support,a thread cutter carried by said bracket and connected to said clampingarm, said clamping arm being movable by upward movement of said bracketto actuate said cutter to sever the thread.

2. A sewing machine, according to claim 1, wherein said cutter comprisesa cutter lever mechanism, a pressure plate supported on said racket,said lever mechanism being pivoted on said pressure plate and beingconnected to said clamping arm and being pivotal thereby to effect thecutting operation.

3. A sewing machine, according to claim 1, including a press plate, avertically movable member carrying said press plate and having a pinportion, a guide carried on said bracket in which said member is movableupwardly and downwardly and including a slot in which said pin portionis engageable and confined for movement within defined limits of saidslot, and spring means urging said pressure plate downwardly away fromsaid bracket, said pressure plate being engageable with the workpieceand carrying said cutter.

4. A sewing machine, according to claim 3, wherein the connectionbetween said clamping arm and said bracket includes a crank pivotallymounted on said clamping arm and having an end pivotally connected to anactuating member connected to said cutter, said crank having a pawlengagement surface, and a ratchet lever pivoted on said bracket andengageable with said pawl to rotate said crank to move said actuatingmember to actuate said cutter when said bracket is moved upwardly by apredetermined amount.

5. A sewing machine, according to claim 4, wherein said cutter isconnected by four-bar linkage comprising said actuating member, saidcrank with said pawl, and said cutter, said cutter including a pivotallever portion included in said four-bar linkage. l

6. A sewing machine, according to claim 4, inc'ludin a bridge pivotallymounted on said bracket, saidratchet lever being pivoted on said bridgeand adjustment means connected to said bridge for adjusting in theposition thereof.

1. A sewing machine comprising a machine frame having a workpiecesupport, a bracket mounted on said frame for pivotal movement upwardlyto a rest position and downwardly to an operative position, a needlemounted on said frame for upward and downward reciprocation below saidsupport, a rotatable shuttle mounted on said bracket overlying saidneedle for cooperative engagement therewith, a clamping arm connected tosaid bracket for movement therewith and pivoted on said frame over saidsupport and having an end adapted to clamp the workpiece on the support,a thread cutter carried by said bracket and connected to said clampingarm, said clamping arm being movable by upward movement of said bracketto actuate said cutter to sever the thread.
 2. A sewing machine,according to claim 1, wherein said cutter comprises a cutter levermechanism, a pressure plate supported on said racket, said levermechanism bEing pivoted on said pressure plate and being connected tosaid clamping arm and being pivotal thereby to effect the cuttingoperation.
 3. A sewing machine, according to claim 1, including a pressplate, a vertically movable member carrying said press plate and havinga pin portion, a guide carried on said bracket in which said member ismovable upwardly and downwardly and including a slot in which said pinportion is engageable and confined for movement within defined limits ofsaid slot, and spring means urging said pressure plate downwardly awayfrom said bracket, said pressure plate being engageable with theworkpiece and carrying said cutter.
 4. A sewing machine, according toclaim 3, wherein the connection between said clamping arm and saidbracket includes a crank pivotally mounted on said clamping arm andhaving an end pivotally connected to an actuating member connected tosaid cutter, said crank having a pawl engagement surface, and a ratchetlever pivoted on said bracket and engageable with said pawl to rotatesaid crank to move said actuating member to actuate said cutter whensaid bracket is moved upwardly by a predetermined amount.
 5. A sewingmachine, according to claim 4, wherein said cutter is connected byfour-bar linkage comprising said actuating member, said crank with saidpawl, and said cutter, said cutter including a pivotal lever portionincluded in said four-bar linkage.
 6. A sewing machine, according toclaim 4, including a bridge pivotally mounted on said bracket, saidratchet lever being pivoted on said bridge and adjustment meansconnected to said bridge for adjusting in the position thereof.